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- D'Errico, G., et al.
(författare)
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Comparison of well-mixed and multiple representative interactive flamelet approaches for diesel spray combustion modelling
- 2014
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Ingår i: Combustion Theory and Modelling. - : Informa UK Limited. - 1364-7830 .- 1741-3559. ; 18:1, s. 65-88
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Tidskriftsartikel (refereegranskat)abstract
- The application of detailed chemistry to the computational fluid dynamics simulation of combustion process in diesel engines has many potentials, including the possibility to predict auto-ignition, diffusion flame structure, stabilisation and soot formation in a wide range of operating conditions, also taking into account the effects of different fuel types. Among the approaches that were proposed over the years, the ones that are mostly used in practical calculations can be divided into two main categories: the first assumes each cell to be a well-stirred reactor, while the second employs the flamelet assumption to describe both auto-ignition and turbulent diffusion flame propagation. Despite the fact that both types of model have been widely validated over the years, a detailed comparison between them appears to be very useful in order to understand better the relevant parameters governing auto-ignition, flame stabilisation and the formation of pollutant emissions. This work is focused on a comparison of two different combustion models that were recently implemented by the authors in an open-source code. The first assumes each cell to be a homogeneous reactor and neglects interaction between turbulence and chemistry, while in the second, multiple laminar flamelets are used to represent the structure of a turbulent diffusion flame. Suitable techniques for online reaction rate tabulation and chemical mechanism reduction are also incorporated, to make the use of bigger mechanisms possible (up to 150 species). The two models are compared and validated by simulating constant-volume diesel combustion in a wide range of operating conditions, including variations of ambient temperature and oxygen concentration. Comparison between the computed and experimental data on flame structure, auto-ignition and flame lift-off enables an understanding of the main relevant differences between the models in the way both auto-ignition and flame stabilisation processes are predicted.
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| 4. |
- Kelkensberg, F., et al.
(författare)
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Attosecond Control in Photoionization of Hydrogen Molecules
- 2011
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Ingår i: Physical Review Letters. - 1079-7114. ; 107:4
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Tidskriftsartikel (refereegranskat)abstract
- We report experiments where hydrogen molecules were dissociatively ionized by an attosecond pulse train in the presence of a near-infrared field. Fragment ion yields from distinguishable ionization channels oscillate with a period that is half the optical cycle of the IR field. For molecules aligned parallel to the laser polarization axis, the oscillations are reproduced in two-electron quantum simulations, and can be explained in terms of an interference between ionization pathways that involve different harmonic orders and a laser-induced coupling between the 1s sigma(g) and 2p sigma(u) states of the molecular ion. This leads to a situation where the ionization probability is sensitive to the instantaneous polarization of the molecule by the IR electric field and demonstrates that we have probed the IR-induced electron dynamics with attosecond pulses.
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| 5. |
- Kelkensberg, F., et al.
(författare)
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XUV ionization of aligned molecules
- 2011
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 84:5, s. 051404-051404
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Tidskriftsartikel (refereegranskat)abstract
- New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO2 molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.
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| 6. |
- Lucchini, Roberto G., et al.
(författare)
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Inverse association of intellectual function with very low blood lead but not with manganese exposure in Italian adolescents
- 2012
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Ingår i: Environmental Research. - : Elsevier BV. - 1096-0953 .- 0013-9351. ; 118, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pediatric lead (Pb) exposure impacts cognitive function and behavior and co-exposure to manganese (Mn) may enhance neurotoxicity. Objectives: To assess cognitive and behavioral function in adolescents with environmental exposure to Pb and Mn. Methods: In this cross sectional study, cognitive function and behavior were examined in healthy adolescents with environmental exposure to metals. The Wechsler Intelligence Scale for Children (WISC) and the Conners-Wells' Adolescent Self-Report Scale Long Form (CASS:L) were used to assess cognitive and behavioral function, respectively. ALAD polymorphisms rs1800435 and rs1139488 were measured as potential modifiers. Results: We examined 299 adolescents (49.2% females) aged 11-14 years. Blood lead (BPb) averaged 1.71 mu g/dL (median 1.5, range 0.44-10.2), mean Blood Manganese (BMn) was 11.1 mu g/dL (median 10.9, range 4.00-24.1). Average total IQ was 106.3 (verbal IQ= 102, performance IQ= 109.3). According to a multiple regression model considering the effect of other covariates, a reduction of about 2.4 IQ points resulted from a two-fold increase of BPb. The Benchmark Level of BPb associated with a loss of 1 IQ-point (BML01) was 0.19 mu g/dL, with a lower 95% confidence limit (BMLL01) of 0.11 mu g/dL. A very weak correlation resulted between BPb and the ADHD-like behavior (Kendall's tau rank correlation=0.074, p=0.07). No influence of ALAD genotype was observed on any outcome. Manganese was not associated with cognitive and behavioral outcomes, nor was there any interaction with lead. Conclusions: These findings demonstrate that very low level of lead exposure has a significant negative impact on cognitive function in adolescent children. Being an essential micro-nutrient, manganese may not cause cognitive effects at these low exposure levels. (c) 2012 Elsevier Inc. All rights reserved.
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| 10. |
- Rentschler, Gerda, et al.
(författare)
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ATP13A2 (PARK9) polymorphisms influence the neurotoxic effects of manganese.
- 2012
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Ingår i: NeuroToxicology. - : Elsevier BV. - 1872-9711 .- 0161-813X. ; 33:4, s. 697-702
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: A higher prevalence of individuals affected by Parkinsonism was found in Valcamonica, Italy. This may be related to ferro-alloy smelters in the area, releasing manganese (Mn) in the air, soil and water for about a century. There exists individual susceptibility for Mn neurotoxicity. AIM: To analyse how polymorphism in genes regulating Mn metabolism and toxicity can modify neurophysiological effects of Mn exposure. MATERIALS AND METHODS: Elderly (N=255) and adolescents (N=311) from Northern Italy were examined for neuromotor and olfactory functions. Exposure to Mn was assessed in blood and urine by atomic absorption spectroscopy and in soil by a portable instrument based on X-Ray fluorescence technology. Polymorphisms in the Parkinson-related gene ATPase type 13A2 (ATP13A2, also called PARK9: rs3738815, rs2076602, rs4920608, rs2871776 and rs2076600), and in the secretory pathway Ca(2+)/Mn(2+) ATPase isoform 1 gene (SPCA1: rs218498, rs3773814 and rs2669858) were analysed by TaqMan probes. RESULTS: For both adolescents and elderly, negative correlations between Mn in soil and motor coordination (R(s)=-0.20, p<0.001; R(s)=-0.13, p=0.05, respectively) were demonstrated. Also among adolescents, negative correlations were seen between Mn in soil with odor identification (R(s)=-0.17, p<0.01). No associations were seen for Mn in blood or urine. ATP13A2 polymorphisms rs4920608 and rs2871776 significantly modified the effects of Mn exposure on impaired motor coordination in elderly (p for interaction=0.029, p=0.041, respectively), also after adjustments for age and gender. The rs2871776 altered a binding site for transcription factor insulinoma-associated 1. CONCLUSIONS: ATP13A2 variation may be a risk marker for neurotoxic effects of Mn in humans.
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